1. Field of the Invention
The present invention relates to optical disc apparatuses such as a digital video disc or digital versatile disc (DVD) player, a DVD-ROM drive, and a DVD recorder, an optical disc recording method, and an optical disc.
2. Description of the Related Art
In recent years, an optical disc has been developed in which video, audio, sub-picture or the like is coded and recorded with high density. It is supposed that story data of a plurality of simultaneously proceeding stories are recorded in a case where information such as movies are recorded on this optical disc. It is also supposed that the same event proceeding simultaneously is photographed from a plurality of angles to record multi-angle scene in a case where information such as movies are recorded on the optical disc.
An optical disc producer has options such as a case where both the first and second stories are composed and shown to audiences, a case where the first story is to be mainly shown to audiences, and a case where the second story is to be mainly shown to audiences. Any of them has to be selected and produced in conventional movie production. This also applies to the above-described first and second scenes. Here, if the audience can freely select both the first and second stories or either of them, a degree of freedom is enhanced for the producer in the production.
In recent years, an optical disc recording/reproducing apparatus has been developed in which a plurality of simultaneously proceeding stories or scenes are recorded beforehand in a case where information like the movies is recorded, and the audience can freely select them at a playback time.
Here, in a case where the data of the plurality of stories or scenes are recorded in the optical disc, the data is preferably recorded in such a manner that processing of the data becomes convenient at the playback time. For example, it is supposed that the story data of the first and second stories is recorded in series. When only one of the stories is reproduced at the playback time, it is necessary to jump to a recording area of the other story. However, when the other story has a short time, physical movement is little in picking up the story, and there is no problem. However, when the other story has a long time, the physical movement is large in picking up the story. Therefore, interruption or disturbance sometimes occurs in the reproduced video.
It has been proposed to provide a disc recording apparatus and method in which a recording structure of an interleaved block is devised such as a multi-scene, further a reproduction process system is devised, accordingly burdens on hardware are reduced, and the number of streams is easily increased (see e.g., Japanese Patent No. 2857119 (paragraphs 0094 to 0110, FIGS. 22 to 24)).
This apparatus has a data region in which data to be decoded is recorded, as well as management data necessary for reproducing the recorded data of the data region. The data region also includes control data, and has an interleaved block section in which video signals of a plurality of scenes are divided/distributed into a plurality of interleaved units, respectively, and the interleaved units of the respective scenes are mixed/arranged on a recording track. The control data is included in each interleaved unit. The apparatus reproduces a recording medium in which the following are described: information indicating that the interleaved units are mixed/arranged; and a logical address of the next interleaved unit which is the next jumping end for each scene. Means for controlling the system comprises: means for reading the control data which is included in the interleaved unit every time the interleaved unit is reproduced, and recognizing the information indicating that the interleaved units are mixed/arranged, and the logical address of the next interleaved unit which is the next jumping end for each scene; and means for controlling a read position of the data of the recording medium in such a manner as to change a reproduction stream of the interleaved unit with reference to the logical address of the next interleaved unit for each scene included in the control data, when operation information for scene switching is given. The jumping end of the next interleaved unit for each scene is newly recognized from the control data which is acquired in the read position and which is included in the interleaved unit to wait for the scene switching. By the above-described means, management of the scene switching is facilitated, the burden on the hardware are reduced, design of the recording apparatus is facilitated, and prices are lowered.
Usually, read speed of the data from an ECC processing unit is substantially constant, but the video data is recorded in a variable speed system, and therefore the read speed required by a decoder fluctuates in accordance with contents of pictures. In a case where the data is recorded in the multi-scene system, the data is not continuously recorded in the disc, and is intermittently recorded in discontinuous places. Therefore, the data is not continuously read, but the decoder continuously requires the data. To absorb this difference, the reproduced data from an ECC processing unit is once stored in a track buffer, and an output of the track buffer is supplied to the decoder. A size of the interleaved unit is determined in such a manner as to satisfy conditions on which the data is continuously output from the track buffer, that is, the data is supplied to the decoder without being interrupted. The size of the track buffer is determined in such a manner that the track buffer output data is not interrupted, even when the recording apparatus performs a kickback operation and subsequently the interleaved unit jumps. In the kickback process, data for a predetermined section read up to now is again read. The process indicates a function of compensating for data dropout, even when data overflows from the track buffer.
A DVD standard (see, e.g., Standard ECMA-267 120 mm DVD-Read-Only Disc (3rd Edition-April 2001)) using the above-described technique broadly spreads, and is favorably received. Additionally, in recent years, home display devices for high-definition (HD) images have started spreading, and studies of information recording mediums have also been advanced for the high-definition (HD) images. In the conventional DVD-Video standard, it is possible to record the movie having a standard length and standard definition (SD) on a DVD-ROM having a single layer, but in recent years, by progress of a motion picture image compression technique, the high-definition (HD) image having about four times pixels can be compressed into an approximately doubled data amount on average. Consequently, it is possible to store the movie on a DVD-ROM having dual layers. However, this means that the data amount is doubled on average, and the data amount is partially tripled. Therefore, the conventional speed is tripled as a data transfer rate Vo in supplying the data from the track buffer to the decoder. The conventional rate needs to be also tripled as a data transfer rate Vr in supplying the data from the ECC processing unit to the track buffer. In the conventional DVD-Video standard, the data transfer rate Vo of the multi-scene part is set to a value smaller than that of a part other than the multi-scene part, but there has been a demand for increasing of the data transfer rate Vo from image quality. When the data transfer rate Vo increases, the size of the interleaved unit increases, and a jumping distance needs to be lengthened.
Additionally, since a linear recording density is constant in many optical discs including the DVD-ROM, a rotation speed needs to be changed with radius in order to read the information at a constant data transfer rate Vr. As a rotation control system of the optical disc, a CLV system is used in the DVD-ROM, and a ZCLV system is adopted in a DVD-RAM. In the CLV system, a rotation number is changed (the number is raised toward an inner side) in accordance with the radius in such a manner that the recording/reproducing linear speed is constant on the whole surface of the disc, and the data is recorded/reproduced with a constant linear recording density on the whole surface of the disc to secure a recording capacity. A recording/reproducing frequency is also constant. In the ZCLV system, the disc is divided into a plurality of donut-shaped recording regions (zones) in a radial direction, a CAV system (the rotation number is set to be constant) is used in each zone, and the number of sectors per track of each zone is increased toward an outer periphery. The rotation number is constant in the zone, but differs between the respective zones. The disc rotates at a low speed in the outer peripheral zone. However, the linear speed is substantially constant over the whole surface of the disc.
The changing of the rotation speed in accordance with the radius is realized by controlling a spindle motor. However, when a torque of the spindle motor is set to be constant, a time required for changing the rotation speed in the equal radius is substantially proportional to the data transfer rate Vr and the jumping distance. In reality, as a general characteristic of the motor, when the rotation speed rises, viscosity resistance and windage loss increase. Therefore, when the rotation is speeded up, the torque decreases which is usable in acceleration/deceleration of the disc rotation speed.
In the conventional DVD-Video standard, the disc rotation speed can be followed up (a time required for the follow-up is several tens of msec) by the end of the jumping. However, when the above-described demand is accepted that the disc rotation speed is tripled and the jumping distance is also lengthened, it is difficult to increase the torque of the spindle motor. Therefore, it is difficult to maintain the linear speed, that is, a read-out speed at a desired speed when the jumping ends. Especially in a portable apparatus, there is a limitation to a peak power usable for operating a battery. To increase the peak power, a battery size is increased, that is, the apparatus is enlarged, this results in a weight increase, and a commercial property is impaired. Therefore, the increasing of the torque of the motor is non-realistic.
When the jumping is performed from the outer periphery to the inner periphery at the playback time of a dual-layer disc, the disc rotation speed has to be raised. However, when the disc cannot be tracked because of torque shortage, a possibility occurs that the data transfer rate Vr lowers below an assumed reference value, the track buffer becomes empty, and the image is interrupted. Especially, this is an important problem in a high-definition video, because the video has a large data amount, and the dual-layer disc is often used.
Moreover, in the present DVD-ROM drive in which high-speed reproduction is possible, it is supposed that the disc recorded at a constant linear speed is played back using a system (CAV system) in which the disc is rotated at a constant rotation speed, not a constant linear speed (CLV system). In this case, the read data transfer rate Vr is secured to be three or more times. Assuming that the rate of the inner periphery is set to be three times, the linear speed of an outermost periphery is about 7.3 times. When this system is usable, the above-described problem is eliminated.
However, for example, the read-out speed assured by the standard of the present DVD-ROM is a double speed. When the reproduction at the double speed is assumed, mechanical characteristics are determined such as disc warp and eccentricity. When there is the disc warp or eccentricity, an objective lens actuator needs to generate a power for the follow-up. However, since the acceleration generated by distortion or eccentricity is proportional to the square of the linear speed, it is necessary to generate a power 64 times the power at the double speed, for example, at an eight-times speed. In actual, it is difficult to generate this large power. Therefore, the high-speed reproduction is difficult depending on mechanical characteristics such as disc warp even in the drive in which high-speed reproduction is possible. Therefore, in this case, the reproduction speed is lowered. That is, the high-speed reproduction is possible in a case where the disc warp or eccentricity is sufficiently small with respect to the standard, but the follow-up is impossible in a case where the warp or eccentricity is large. Therefore, the reproduction speed has to be lowered.
In a disc in which the high-definition (HD) video can be recorded, a maximum value of the disc warp or eccentricity has to be determined in such a manner that the reproduction is possible at a triple speed. However, when considering a manufacturing technique, change with time, cost and the like of the present disc, and performance and cost of an optical disc recording apparatus, it is unrealistic to determine the standard in such a manner as to perform the reproduction in the CAV system in which the innermost periphery indicates the triple speed. The above-described problem cannot be avoided by the reproduction performed in the CAV system.
As described above, the disc rotation speed needs to be raised in the conventional optical disc unit for the HD image. In this case, there is a possibility that the data transfer rate cannot be kept constant or higher in reading the data from the disc or writing the data into the track buffer.